NPSH Available (Pump)

Calculate the net positive suction head available at a pump and check the margin against the required NPSH to avoid cavitation, free online.

Absolute pressure at the liquid surface (kPa)

Vapour pressure of the liquid (kPa)

Density (kg/m³)

Static head above pump (m, negative if below)

Suction friction losses (m)

NPSH required by the pump (m) — optional (optional)

About this calculator

NPSHa = (P_atm − P_vapour) ÷ (ρg) + z_suction − h_friction, where z is positive when the liquid level is above the pump. To avoid cavitation NPSHa should exceed NPSHr by a safety margin (commonly 0.5 m or 10–20%).